VSX-1 AND VSX-2 - 2 CHX10-LIKE HOMEOBOX GENES EXPRESSED IN OVERLAPPING DOMAINS IN THE ADULT GOLDFISH RETINA

The genetic linkages of the murine ocular retardation mutation with th e Chx10 gene and the murine small eye mutation with the Pax-6 gene has demonstrated the importance of Paired class homeobox genes in the dev elopment of the mammalian retina. Previously, we identified a Paired-c lass homeobox gene, Vsx-1, whose expression in the adult goldfish reti na is restricted to the inner nuclear layer (INL) and to postmitotic, differentiating progenitor cells in the growth zone at the retinal per ipheral margin, where neurogenesis continues throughout life. Here, we report the molecular cloning and expression pattern of a new Paired c lass homeobox gene, Vsx-2, in the adult goldfish retina. Like Vsx-1, V sx-2 expression is highly restricted to the retina in the adult goldfi sh and overlaps with Vsx-1 expression in the mature INL. At the periph eral margin, Vsx-2 is expressed in mitotically active neuronal progeni tors and is downregulated as these cells become postmitotic and begin to differentiate. Comparison of the amino acid sequences of Vsx-2, Vsx -1, Chx10, and C. elegans ceh-10 reveal a conserved homeodomain and a unique domain termed the CVC domain. The similarities of the Vsx-2, Vs x-1, and Chx10 expression patterns suggest that genes containing the C VC domain have conserved functions during retinal development in verte brates. (C) 1997 Wiley-Liss, Inc.